Beach erosion history from satellite shoreline analysis
See how a coastline has moved over decades, and how fast.
Beach erosion history reconstructs shoreline positions from archived satellite imagery to show where the coast has advanced or retreated. It gives rates of change, not just a before-and-after picture. It is useful for coastal planning, setback decisions and checking the effect of structures.
Landsat archive reaches back to the 1980s
Set by pixel size at medium resolution
Per transect along the coast
Remote analysis
What is a beach erosion history?
A shoreline is not a fixed line. It shifts with the tide, waves and season, so a single image cannot say whether a beach is eroding. The method uses many images, extracts the waterline from each using spectral indices that separate water from sand, and corrects it for the tide level at the time of capture.
The corrected shorelines are then compared along lines drawn at right angles to the coast, called transects. Statistical methods such as linear regression give an average rate of change in metres per year, with a confidence interval, for each transect.
The result shows where retreat is concentrated, whether it is steady or episodic, and how changes follow storms, harbour works, dredging or river mouths. Higher-resolution imagery refines recent positions.
Accuracy is limited by pixel size, tide correction and image availability. Changes smaller than a pixel are hard to detect, so the method suits trends over years rather than single events. Surveyed profiles from drone or GNSS surveys are used when volumes are needed.
How it works
Collect
Gather all usable archive images for the coastline over the chosen period.
Extract
Detect the waterline in each image using water indices.
Correct
Adjust each shoreline for tide level at the time of capture.
Measure
Calculate change along transects and fit trends.
Map
Present rates of erosion and accretion as maps and charts.
What you receive
Maps
a. Shoreline position by year
b. Erosion and accretion rate map
Data
a. Transect tables with rates and uncertainty
b. Shoreline vectors for GIS
Reporting
a. Method and limitations summary
Where it is used
Coastal planningSet building setbacks using observed retreat rates.
Beach nourishmentIdentify where sand is lost and how fast.
Port and breakwater effectsSee how structures change nearby shorelines.
Tourism and resortsAssess the long-term viability of beachfront sites.
Climate adaptationQuantify existing trends before projecting sea-level rise.
Insurance and riskSupport exposure assessments of coastal assets.
Frequently asked questions
How far back can the history go?
Landsat imagery starts in the 1980s in most regions, so records of up to about 40 years are possible. Cloud cover and gaps in the archive limit some locations.
How accurate are the shoreline positions?
Medium-resolution imagery gives positions to roughly a pixel, around 10 to 30 m, though trends over many images are more reliable than any single position.
Does it measure sand volume?
No. It measures the position of the waterline. Volumes need beach profile or topographic survey, for example by drone.
Can it separate storms from long-term trends?
Partly. Time series show sudden steps after storms against gradual change, but limited image frequency can miss short events.
How fast is your coastline moving?
Send us the stretch of coast and we will scope a shoreline change study.
